[m4rtink]

Yeah, most likely engine bay fire taking out systems one by one. Would be interesting to compare the telemetry cutoff with the video of explosion if possible. That could indicate if the fire even triggered an explosion, flight termination being activated or just reentry heating making the tanks explode.

[s1artibartfast]

Who knows where it started, but the fire was definitely in the payload bay in front of the header tanks if seen through the flap actuators during ascent, after speration at ~7:45 min

[Culonavirus]

The single instance of a fire that could be seen in the stream was in the hinge area of a bottom flap.